Oxygen reduction on potentiodynamically formed Pd/TiO2 composite electrodes

By multiple potentiodynamic polarization of polished titanium surface in an aqueous PdCl2 solution, a thin composite Pd/TiO2 layer was formed, consisting of Pd submicron particles grown through a nanometer-thin surface TiO2 layer. The real surface area of Pd was determined by cyclic voltammetry in nitrogen purged 0.1 mol dm−3 HClO4. The oxygen reduction reaction on the Pd/TiO2 layer in 0.1 mol dm−3 KOH and 0.1 mol dm−3 HClO4 solutions has been studied using rotating disc electrode (RDE) voltammetry. Comparing to the best palladium or palladium based catalysts published thus far, the Pd/TiO2 composite yielded similar or higher (in acidic solution) or discernible higher (in alkaline solution) rate of oxygen reduction.This was found to be mostly due to the high surface area of Pd particles, but, to some extent, due to the influence of TiO2 support itself.

► Pd/TiO2 composite layer was formed potentiodynamically on Ti surface. ► The surface roughness factor 24 was obtained, which depends on the number of cycles. ► The Tafel slope of −65 mV was found in 0.1 M KOH, which did not vary with potential. ► Higher exchange current density of ORR than on any bulk Pd electrode was found.